added RwLock to lock module

fixed missing state variable for waiting readers

fixed deadlocking problem with new WaiterSet type

added ticketing system

added tests

renamed ticket to phase in RwLockReadFuture

Author: rj-calvin

futures-util/src/lock/mod.rs

@@ -25,3 +25,12 @@ mod bilock;
 #[cfg(not(futures_no_atomic_cas))]
 #[cfg(feature = "std")]
 mod mutex;
+
+#[cfg(not(futures_no_atomic_cas))]
+#[cfg(feature = "std")]
+mod rwlock;
+#[cfg(not(futures_no_atomic_cas))]
+#[cfg(feature = "std")]
+pub use self::rwlock::{
+    RwLock, RwLockReadFuture, RwLockReadGuard, RwLockWriteFuture, RwLockWriteGuard,
+};